Tuning the Photophysical and Electrochemical Properties of Aza‐Boron‐Dipyridylmethenes for Fluorescent Blue OLEDs

Abstract

A series of substituted aza-boron-dipyridylmethene (aD) compounds are demonstrated as fluorescent dopant emitters in blue organic light emitting diodes (OLEDs). Replacing the meso-carbon of a dipyridylmethene dye with nitrogen to form the aD chromophore leads to a destabilization of the highest occupied molecular orbital in aD, as evidenced both from their experimentally determined photophysical and electrochemical properties. These properties are consistent with theoretical calculations of the molecular energetics. These aD derivatives emit violet to blue light, peaking between 400 and 460 nm with photoluminescent quantum yields over 85%. The aD compounds have small energy differences (<400 meV) between their singlet and triplet excited states. OLEDs fabricated with an aza-boron-dipyridylmethene emitting fluorophore give an external quantum efficiency of 4.5% on glass substrates, close to the theoretical maximum for fluorescent OLEDs.

Toward rational design of TADF two-coordinate coinage metal complexes: understanding the relationship between natural transition orbital overlap and photophysical properties

“…The overlap value was numerically evaluated as described previously. 55 Table 2 gives the NTO overlap values for the S 1 and T 1 (ICT) states, 1 ICT and 3 ICT, respectively. As observed previously, 56 the NTO overlap is larger for the triplet state than the singlet state, however the trends are the same as a function of metal, i.e.…”

Recent advances in the synthesis of luminescent tetra-coordinated boron compounds

“…Many of the newly synthesized fluorophores displayed attractive photophysical properties, some of them showed interesting aggregation induced emission, mechanochromism and solvatochromism. The tetra-coordinated boron compounds as NIR 65 and blue 247 OLEDs, sensitizers for singlet oxygen, 95 circularly polarized luminescence, 229 and two photon absorption with high brightness 248 have emerged as excellent developments of these materials. In some instances the boron-based materials have shown better properties over pure organic materials.…”

A periphery hindered strategy with a dopant and sensitizer for solution-processed red TSF-OLEDs with high color purity

“…31–33 Nevertheless, serious aggregation fluorescence quenching is inevitable in the solid state of BODIPY; this quenching originates from the relatively strong intermolecular stacking and small Stokes shifts that induce forceful self-absorption behavior; it distinctly limits the compound's application in the optoelectronic field, especially in OLEDs. 34–36 To solve this issue, BODIPYs can be used as fluorescent dopants diluted with TADF sensitizer, whereby 25% of the S 1 exciton can be utilized to realize narrowband emission via Förster energy transfer (FET) from TADF sensitizer to the BODIPY dopant 37,38 as depicted in Fig. 1.…”